1. Technical Field
The present invention relates to a wobble plate type compressor with a variable displacement mechanism, and more particularly to a cylindrical member which is formed with a central hole and which supports the wobble plate at a variable inclination angle.
2. Description Of The Prior Art
A wobble plate type compressor which reciprocates a plurality of pistons by converting the rotational movement of a cam rotor into nutational movement of a wobble plate is well known in the art. Changing the inclined angle of the wobble plate changes the stroke length of the pistons and therefore changes the displacement volume of the cylinder. In U.S. Pat. No. 4,846,049, herein incorporated by reference in its entirety, a wobble plate is proximately disposed on a variable angle rotating cylindrical member. The cylindrical member is hingedly connected to a rotor which is fixed on the drive shaft. A central hole is formed through the cylindrical member so that a drive shaft can extend through the central hole. The rotor permits the inclined angle of the cylindrical member to be varied. The inclination angle of the cylindrical member depends upon the pressure difference between the crank chamber and the suction chamber.
In this structure, the inclined angle of the cylindrical member must be easily variable in response to changes in the pressure difference between the crank and suction chambers. Thus, the shape of the central hole is elongated. However, it is difficult to accurately machine the elongated shape.
A working tool is used to form the central hole. Since the shape of the central hole is elongated, the inclined angle of the rotational axis of the working tool must be continuously and smoothly changed within a range of angles to form the shape of the elongated hole. The working tool must not move in a stepwise fashion. However, since the working tool must form the shape of the hole while moving its rotational central axis, it is necessary to provide a complicated control for the movement of the rotational central axis of the work tool to obtain the desired accuracy of the shape of the central hole. Thus, the manufacturing costs for forming the complicated shape of the central hole are very high.